Short Wave - Mouse Vs Scorpion: A Mind-Blowing Desert Showdown

Episode Date: March 5, 2020

This one doesn't end the way you'd expect. Inspired by the Netflix documentary series "Night On Earth," we learn everything we can about a mouse and scorpion who do battle on the regular — from two scientists who study them: Ashlee Rowe at the University of Oklahoma and Lauren Esposito at the California Academy of Sciences. If you have Netflix, you can watch the critters clash about 18 minutes into the episode 'Moonlit Plains' here. Read more about Lauren's work with scorpions here, and Ashlee's work with grasshopper mice here. And you can learn more about grasshopper mouse vocalizations from Northern Arizona University's Bret Pasch here.Email the show at [e-mail] pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. I don't know about you, but watching prestige nature documentaries is my idea of a wild Friday night. The scorching sun means many desert animals only come out at night. And there's a new one on Netflix, narrated by the Amazing Samara Wiley, called Night on Earth, where a little desert mouse. A tiny grasshopper. For mouse, comes face to face with a scorpion. Might want to steer clear. This is in the Sonoran Desert.

Well, the Sonoran Desert is in, like, western New Mexico, and sort of extends down into Sonora, Mexico. That's Lauren Esposito. I'm the curator of arachnology at the California Academy of Sciences. Scorpions, aka. A.K.A. Arachnids. Team Scorpion all the way. Yeah.

You see where this is going. Hey, Lauren. How's it going? Oh, I'm so excited. That's Ashley Rowe. I'm an assistant professor in the biology department at the University of Oklahoma. Ashley studies the grasshopper mouse, which is, I believe this is the scientific term, adorable. They're sort of like, they look like Mickey Mouse, these big ears and these big eyes and these long whiskers,

and they just look really innocent and cute. We absolutely had to get Ashley and Lauren together so we could learn everything about what happens next. Many animals try to avoid venomous scorpions. Everybody's got to eat, you know. But not this little rodent. In a flash, the mouse attacks the scorpion. He's a scorpion eating specialist. Completely ignores like multiple stings to the face.

His body can block the pain from even the most lethal scorpion toxins. And then rips the scorpion's tail off. Sting disarmed. Eat the scorpion. Scorpion dispatched. And then howls into the sky. He claims his territory. That was his tiny scream.

Yeah, they howl. It's pretty adorable. Even I have to admit that. This episode, a mouse versus scorpion showdown, that seriously will blow your mind. I'm Maddie Safia, and this is Shortwave, the Daily Science podcast from NPR. Quick note here on the mouse scorpion throat. In the Netflix show, that scorpion is called the giant hairy scorpion. For the purposes of this scholarly discussion, we've substituted the Arizona bark scorpion,

also a scorpion, this mouse likes to eat, but way more intense venom. And therefore, cooler. All right, y'all, are you ready to throw down? Ready. Yes, ready. So as you both know, we don't want to make this feel too competitive. It's just a low-key, easygoing, science-based conversation about two mortal enemies locked in a battle for survival. Let's get ready to rumble.

In one corner from the dry and fearsome snoring desert weighing in at... Ashley, how much of these mice weigh? Anywhere between 20 to 50 grams. About an ounce. It's the grasshopper mouse. And in the other corner from a little dirt hole under a rock down the hill, the stinger in the ringer. It's the Arizona bark scorpion.

So we are going to break down this fight between these two little batties and learn as much as we can about them in the next ten minutes. Sound good? I think we can do it. All right. So Ashley, this grasshopper. It's going out searching for scorpions. Is this like its primary snack or what is it, what is it going after out there? So in some areas, that is its primary snack. Yeah. Grasshopper mice are distributed throughout short grass prairies and deserts in North America.

So in some areas, they'll eat spiders, scorpions, lizards, small birds, they will eat other mice. Birds? They're going up in. Yeah, birds, small birds. Birds, birds, birds was the one that really shocked me. It's hard to imagine this tiny little mouse eating a bird. Well, they do actually if you, like you can't house two males together. The males are really aggressive. So they will kill each other. Yeah. Do they eat each other when they kill each other?

They do. They eat the brain out. No, they eat the brain out? They do. Oh, like, no, that's so crazy. Yeah. I understand that podcasting is a audio medium, but I would strongly suggest our listeners at this point pull up a picture of this mouse because it's so cute. It does not fit the bill.

No, it doesn't. Like, you see a picture of them and you're like, oh, this is a really adorable mouse. And then you learn that they kill each other and eat their brains out. No. Do not be fooled. Don't be fooled. Okay, okay. So, Lauren, when the battle starts, it's possible that the scorpion is ready with, like, a particular kind of venom for this situation.

I didn't know that they had different types of venom. Yeah. Well, so actually, like, one single individual scorpion can produce up to 200 unique compounds and it's cocktail of venom. And we have some preliminary evidence suggesting that they're able to express different parts of that cocktail in different circumstances. So if they're trying to defend themselves, they might be using the more expensive peptides that cause pain. Or if they're trying to capture some prey, they might be using some of the less metabolically costly things like salts and enzymes that is all they really need to break down a cricket. So cool. So, you know,

these scorpias don't get enough credit out here. They're making different types of Venom. Yeah, when you think about it, these scorpions are really small. And when they're trying to subdue their prey, they just need to paralyze it really quickly so it can't get away. But when they're trying to defend themselves from their predators, what they really want to do is deliver a stinging blow that just stuns the predator and gets them dropped so that they can escape. And I think what Ashley's referring to is this idea, this hypothesis that people have proposed called the Venom Conservation hypothesis, which basically says, like, if your body has to produce things and those things cost you energy to produce, you want to use the least amount

in any given circumstance so you don't want to waste all your energy. Honestly, same. You know what I mean? I'm never trying to do too much. I'm never trying to... Like I don't want to walk that far to the gym, to be honest. Okay, so arguably one of the coolest parts of this is that the scorpion gives the mouse the old like one, two, with a tail. Like a sting? Is sting? Is sting the right term? Yeah, sting. All right. So just pops him, boom, boom, with some sting vibes. After that, the mouse is like, you're going to have to do better than that scorpion. So, Ashley, what is going on? Well, the short answer is that the mouse has evolved resistance to the painful toxins that are in the venom.

And so they can get stung multiple times at their face. But the mice at first, they just groom a little bit. Like, it is irritating. They're irritated by it. But then it's like the pain is just over. And then they just go back in for the attack. And then they just keep biting. They get a ferocious look in their eyes.

Yeah. And Lauren, like, just to be clear, Arizona bark scorpions are not producing joke venom. No. It's pretty potent, right? Yeah, so they can produce venom that could potentially kill like a small child. It's no joke. I mean, it's really serious venom. And in some of their close relatives that live in, like, Northern Mexico, those species are producing venom that could kill an adult, like a human.

Yeah, yeah. We should say that it's not like it just is resistant or whatever to this potential venom. Ashley, it makes the mouse more powerful in a way. What? Tell me. No, it's crazy. So when the mice get stung, their pain pathway, or the sensory neurons that make up their pain pathway, they're modified to the proteins in the venom actually block those pain signals. They bind to those sensory neurons, and they actually block the pain signals.

Then they're actually less sensitive to other painful stimuli after they've been stung. It's like the venom becomes an analgesic for them. It becomes a pain blocker. I mean, Lauren, that's pretty cool. You've got to give that up. I know your team scorpion over there, but it's pretty cool. Like, I'm team scorpion, but it's pretty cool. Like, if I could take something that's supposed to be, like, extremely painful

and turn it into something that makes me not feel any pain anymore, that would be pretty epic. Okay. So, Lauren, you've described this to me as kind of like an evolutionary arms race between scorpion venom and the mouse's ability to resist venom. Tell me about that. Well, what we think is that over time, the scorpions have to evolve stronger and stronger venom as a way to get around and escape these really super vicious, terribly awful mice. And so what happens is over time, the mouse gets stronger, the scorpion gets stronger, and it just increases for all of evolutionary history that these two have been in contact. It's just like a tale as old as time. I think, you know, the really cool thing about this whole arms race story is that it's because of the,

the work that Ashley's been doing that we actually have direct evidence that they're currently engaged in this evolutionary arms race because she's found that different populations are more or less resistant to the scorpions that live with them or in different places. So it's really because Ashley likes to experiment with mice and scorpions that we know they're locked in this battle for life. We see you out here, Ashley Rowe. We see you out here. Okay.

So maybe my favorite part. And I know this isn't necessarily something you guys study is, after the mouse kills and eats this scorpion. He throws his tiny little mouse head back, points his nose at the dark desert sky. He claims his territory. I just love it. It's a very ferocious moment. And if you're out there in the desert at night, especially around dusk, when they first started emerging from their burrows, you can't see them. I mean, it's really hard to actually see one out there.

but you can hear them. They start howling, calling to each other. And it's sort of a, hey, I'm out here. This is my territory. Because they do, they have large territories and they can't always see each other, but they can hear each other. So in this video, obviously the mouse is coming out on top. But give me an idea of like, is that most of the time the case or are the scorpions mostly getting away? What's the situation? So in the real world, we think the scorpions get away some of the time, yeah. And scorpions are amazing in that. They know when there's a predator around, they can sense it. They feel vibrations on the surface of the desert. Yeah. And they've got these slits in scylla on their feet, which are basically like tiny little ears in their feet. They're like vibratory organs that pick up vibrations.

And so a lot of times they can orient themselves to the direction of an oncoming predator or prey that they just feel. feel and they know like how basically how big it is because of how much vibration it's making and which direction it's approaching from. And so they're like ready. God, I can't. These are such cool critters. I don't even. That was great. You just said little ears on their feet. I had not thought about putting it that way. I was struggling like, what are those little, I know they're like, because I know, yeah, these scorpions, when we're out collecting, they know that we're after them. They're fast. They're actually hard to catch. Are they? Ashley, you should just be bringing me.

Yeah, they actually come to Lauren when she calls them at this point. Yeah, I just do a whistle. Just like the scorpion mind. Okay, I've got to take you scorpion hunting with me the next time I go out. Ashley Rowe and Lauren Esposito. By the way, Ashley and other scientists are still trying to better understand the pain-killing abilities of the grasshopper mouse to help design better non-addictive pain killers for humans. If you want to read about that or more on either of these amazing critters,

we've got you covered in the episode notes. This episode was produced by Brent Bachman, edited by Viet Le, and fact-checked by Emily Vaughn. I'm Maddie Safaya, and we're back tomorrow, with more shortwave from NPR.